This invention relates to a hot chamber pressure die casting machine of the type comprising a reservoir for molten metal, a gooseneck, one end of which is adapted to be immersed in the molten metal and the other end of which provides a nozzle having an end surface adapted to be brought into engagement with a back surface of a die set from which a feed passage extends to a die cavity defined by the die set and into which a shot of molten metal is injected by a pump in the gooseneck, the die set being mounted on a back plate and comprising a plurality of dies movably mounted on the back plate between a closed position in which the die cavity is defined and an open position in which an article cast within the cavity can be ejected.
An object of the invention is to provide a new and improved die casting machine of the type described.
In one aspect of the present invention, there is provided a die casting machine of the type described wherein the back plate is provided with a track along which a die closure means is adjustable.
The machine may include a plurality of adjustable die closure means and the track may comprise a single circular track lying in the plane of the back plate.
Hitherto, a separate back plate for each die set to be used with the machine has been required, or, the back plate has been provided with a predetermined number of locations at which the dies of a limited number of die sets can be located. Thus, it has not been convenient to change the die sets where different numbers of dies and or different directions of movement of the dies have been required. The present invention overcomes these problems since one, more than one, or all, of the die closure means may be made adjustable along a track of the desired extent and preferably all the die closure means are mounted on a continuous circular track so that they can be oriented in any desired angular position around the back plate.
Preferably, the die closure means is operable to reciprocate the die between the open and closed positions by a linkage from a drive means, the axes of pivot of the linkage lying in a plane parallel to the plane of the back plate and the drive means may comprise a fluid operated piston and cylinder device.
By providing that the linkage and drive means of the die closure means are oriented in this fashion, the area covered by these means in the plane of the back plate is minimized thus permitting closer proximity between adjacent die closure means than has hitherto been possible since conventionally, the axes of the linkage have been in a plane normal to the plane of the back-plate.
As a result, a core member for the die set may be provided with a closure means between one or more pairs of dies.
Clamping means may be provided to permit securing the die closure means in a desired position along the track.
Although a single continuous circular track is preferred, if desired, separate tracks may be provided for each or for only one or more than one of the closure means and the tracks may extend in any desired direction.
Although in the preferred embodiment the back plate lies in a vertical plane, this aspect of the present invention may be applied to a die casting machine in which the back plate does not lie in a vertical plane.
In order to facilitate ejection of a cast article on the die set when the dies are in their open position, it is desired that the back plate should lie in or near (i.e., within 25.degree. and preferably within 10.degree. or 5.degree. of) a vertical plane. However, it was found that if a vertical or near vertical back plate is used, which results in the back surface of the dies from which the feed passage extends also lying in or near a vertical plane, with a gooseneck having a nozzle in which the passage for metal, adjacent the die set engaging end surface, extends in or near a horizontal plane, then metal tends to run out of the nozzle passage at the end surface when the end surface is moved out of engagement with the die set.
It is accordingly another object of the invention to provide a die casting machine of the type described from which cast articles can be easily ejected and in which the above-mentioned problem of "metal dribble" is overcome or is reduced.
According to a second aspect of the invention, there is provided a die casting machine of the type described wherein the back plate lies in or near a vertical plane and the gooseneck nozzle has a passage, part of which lies in or near a horizontal plane, when the nozzle end surface is engaged with the back surface of the die set, and an end portion which is inclined upwardly from the major part to the end surface of the nozzle.
This arrangement avoids metal dribbling out of the nozzle when the nozzle end surface is moved out of engagement with the back surface of the die set and also permits the provision of nozzle heating means including a conventional electrical heating jacket which is relatively bulky and which could not be provided if the whole of the nozzle were to be inclined upwardly.